Schaub's Passing Rank is #21 (other value rankings #18 DYAR and #19 DVOA [DYAR means a quarterback with more total value. DVOA means a quarterback with more value per play])
Because of lack of any run threat, he is not even ranked in this category.

He's not ranked in which category? You posted both his DYAr & DVOa.... they have him at 20 for QBR, which takes into account play making ability & clutch factor.... different from the NFL passer rating.